• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.307-307
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• 2012

In this study, we investigated that the resistance switching characteristics of Al-doped MgOx films with increasing Al doping concentration and increasing film thickness. The Al-doped MgOx based ReRAM devices with a TiN/Al-doped MgOx/Pt/Ti/SiO2 were fabricated on Si substrates. The 5 nm, 10 nm, and 15 nm thick Al-doped MgOx films were deposited by reactive dc magnetron co-sputtering at $300^{\circ}C$ and oxygen partial ratio of 60% (Ar: 16 sccm, O2: 24 sccm). Micro-structure of Al-doped MgOx films and atomic concentration were investigated by XRD and XPS, respectively. The Al-doped MgOx films showed set/reset resistance switching behavior at various Al doping concentrations. The process voltage of forming/set is decreased and whereas the initial current level is increased with decreasing thickness of Al-doped MgOx films. Besides, the initial current of Al-doped MgOx films is increased with increasing Al doping concentration in MgOx films. The change of resistance switching behavior depending on doping concentration was discussed in terms of concentration of non-lattice oxygen of Al-doped MgOx.

• Journal of Preventive Medicine and Public Health
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• v.53 no.6
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• pp.405-408
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• 2020

In epidemiology, the basic reproduction number (R₀) is a term that describes the expected number of infections generated by 1 case in a susceptible population. At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, R₀ was frequently referenced by the public health community and the wider public. However, this metric is often misused or misinterpreted. Moreover, the complexity of the process of estimating R₀ has caused difficulties for a substantial number of researchers. In this article, in order to increase the accessibility of this concept, we address several misconceptions related to the threshold characteristics of R₀ and the effective reproduction number (R_t). Moreover, the appropriate interpretation of the metrics is discussed. R₀ should be considered as a population-averaged value that pools the contact structure according to a stochastic transmission process. Furthermore, it is necessary to understand the unavoidable time lag for R_t due to the incubation period of the disease.

• Journal of Korean Academy of Nursing
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• v.36 no.6
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• pp.1012-1022
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• 2006

Purpose: The purpose of this phenomenological study was to understand the experiences in the transplantation coordinators' practice. Method: Data was collected through a tape-recorded in-depth interview from nine participants who were transplantation coordinators of their hospitals. It was analyzed using the phenomenological method proposed by Colaizzi(1978). Results: From significant statements, six categories of themes were integrated into the essential structure of the experiences of transplantation coordinators. Six categories of themes were 'continue to be professional during dash this way and rush that', 'burden due to persistent heavy work', 'the uniqueness in family care of the brain-dead patients', 'support of family and a professional group', 'worthiness and achievement of the patients' recovery', and 'establishment of self-confidence as a coordinator'. Conclusion: Although the transplantation coordinators played various roles, they had a conflict in role identity due to poor working environments. The results of this study suggested that development of an educational program, an increase in understanding for the coordinators' role, and institutional support for better working conditions are needed to get professional acknowledgement for transplantation coordinators.

• Korean Journal of Materials Research
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• v.27 no.8
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• pp.409-415
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• 2017

For enhanced cavitation erosion resistance of vessel propellers, an electroless Ni-P plating method was introduced to form a coating layer with high hardness on the surface of Cu alloy (CAC703C) used as vessel propeller material. An electroless Ni-P plating reaction generated by Fe atoms in the Cu alloy occurred, forming a uniform amorphous layer with P content of ~10 wt%. The amorphous layer transformed to (Ni3P+Ni) two phase structure after heat treatment. Cavitation erosion tests following the ASTM G-32 standard were carried out to relate the microstructural changes by heat treatment and the cavitation erosion resistance in distilled water and 3.5 wt% NaCl solutions. It was possible to obtain excellent cavitation erosion resistance through careful microstructural control of the coating layer, demonstrating that this electroless Ni-P plating process is a viable coating process for the enhancement of the cavitation erosion resistance of vessel propellers.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.145.2-145.2
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• 2016

We report the phase transformation of Co thin films on a sapphire substrate induced by laser irradiation. As grown Co films were initially strained and tetragonally distorted. With low power laser irradiation, the surface was ruptured and irregular holes were formed. As the laser power was increased, the films changed into round shape Co nanocrystals with well-defined 6-fold structure. By measuring the XRD of Co nanostructure as a function of laser energy densities, we found that the change of morphological shapes from films to nanocrystals was accompanied with decrease of the tetragonal distortion as well as strain relaxation. By measuring the size distribution of nanocrystals as a function of film thickness, the average diameter is proportional to 1.7 power of the film thickness which was consistent with the prediction of thin film hydrodynamic (TFT) dwetting theory. Finally, we fabricated the formation of size controlling nanocrystals on the sapphire substrate without strain.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.591-598
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• 2014

In this research, magnesium powder was prepared by gas atomizing. Refinement behaviors of magnesium powder produced under different conditions were investigated using a mechanical milling (attrition milling) process. Analyses were performed to assess the characterization and comparison of milled powder with different steel ball sizes and milling times. The powders were analyzed by field emission scanning electron microscope, apparent density and powder fluidity. The particle morphology of the Mg powders changed from spherical particles of feed metals to irregular oval particles, then plate type particles, with an increasing milling time. Because of the HCP structure, deformation occurs due to the existence of the easily breakable C-axis perpendicular to the base, which results in producing plate-type powders. An increase in ball size and the impact energy of the magnesium powder maximizes the effect of refinement. Furthermore, it is possible to improve the apparent density and fluidity according to the smoothness of the surface of the initial powder.

• Journal of The Korean Astronomical Society
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• v.42 no.5
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• pp.125-134
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• 2009

We investigated the circumnuclear region of the Seyfert 2 galaxy NGC 5728, using the CFHT 3.6 m OASIS $[S_{II}]$, $[O_{III}]$ & $H\beta$ spectral images complemented with the IUE spectra. The physical condition of the circumnuclear zone has been derived: the gas density (indicated by $[S_{II}]$6716/31 ratio) around the C core is generally similar to that around the NW core, i.e., $\sim500cm^{-3}$. However, there appears to be evidence of a higher density shell in front of the NW core, $\sim10^4cm^{-3}$ at -250 km $s^-1$. The IUE $Si_{III}$]1892/$C_{III}$]1909 ratio implies a possible presence of a broad emission region of gas densities of $\sim10^{10}cm^{-3}$. The SE cone and surrounding area show several prominent features, while the NW cone does not show any particular structure: we identified three prominent blobs in the SE cone and one possible candidate in the NW cone. The outflow activities exist within the relatively large conic opening angle. We discussed the possibility of inflow or outflow activities of blobs found in the circumnuclear region of NGC 5728. The gas around two cores, two cones, and several blobs, is likely to be excited by the AGN hot source(s).

• Journal of Korean Academy of Nursing
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• v.40 no.1
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• pp.1-13
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• 2010

Purpose: The purpose of this study was to develop evaluation criteria for conversations about medication and to demonstrate conversational analysis with actual dialogues on medication as examples. Methods: This study was a secondary analysis of qualitative research using conversational analysis which showed functional phases and patterns of dialogue about medication (greeting, identifying the patient, medicating, finishing). Nurse-patient conversations were videotaped and transcribed and 75 conversations were used for analysis. Results: Not all functional phases were showed in the conversations about medication. Therefore, conversations about medication can be considered as incomplete dialogues. The evaluation-criteria were represented in terms of the structure and content of the dialogues. Structural evaluation-criteria were the same as the functional phases, as functional stage is the standard for evaluation. The criteria of evaluation for content suggested 3 domains, content, expression, and interaction with 20 items scored on a Likert-type scale of 5-points. Finally, analysis of actual conversations about medication according to the evaluative criteria were provided. Conclusion: The results provide the basic data to develop educational programs and strategies to improve nurses’ competency in conversation about medication.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.253-254
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• 2009

본 연구는 다결정 알루미나 소결체와 사파이어웨이퍼(sapphire wafer)의 견고한 접합을 위해 활성금속 Ti가 함유된 Active Filler Metal을 사용하였고, 이를 브레이징한 후 접합 반응층과 Ti 거동 특성에 관한 것이다. 브레이징 (brazing)은 Ar 분위기 종에 $850^{\circ}C$에서 이행하였으며. 이때 다결정 알루미나, 사파이어와 Active Filler Metal 사이의 접합 반응층을 확인하였다. Active Filler Metal 내어| 존재하는 Ti가 접할 반응층의 양계면에 집중되는 것을 SEM을 이용하여 확인하였다. 또한 EDS Line Scanning을 실시하여 접합부에서 원소들의 분포를 관찰하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.680-686
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• 2006

Tin oxide$(SnO_2)$ thin films were prepared on glass substrate by Plasma Enhanced Chemical Vapor Deposition (PECVD) method. $SnO_2$ thin films were prepared using gas mixture of dibutyltin diacetate as a precursor and oxygen as an oxidant at 275, 325, 375, $425^{\circ}C$, respectively as a function of deposition temperature. The XRD peaks corresponded to those of polycrystalline $SnO_2$, which is in the tetragonal system with a rutil-type structure. As the deposition temperature increased, the texture plane of $SnO_2$ changed from (200) plane to denser (211) and (110) planes. Lower deposition temperature and shorter deposition time led to decreasing surface roughness and electrical resistivity of the formed thin films at $325\sim425^{\circ}C$. The properties of $SnO_2$ films were critically affected by deposition temperature and time.